Fabricating and characterizing oblique polymer structures by electron beam writing on resist-coated SiO₂ wafers

We have successfully fabricated SU-8 materials having oblique structures by a new electron beam technology. We studied the contrast, sensitivity, etching, and thermal properties of SU-8, PMMA, and KrF resists to evaluate their suitability for the fabrication of oblique structures. Among these resists, SU-8 revealed the lowest contrast ratio, highest throughput, and best thermal stability, and so it became the candidate material for patterning the oblique structures. The technique we have developed involves five regional exposures of a thick SU-8 resist layer with various electron beam dosages. Furthermore, we discuss the surface morphology, reaction mechanism, and hydrophobicity after subjecting the SU-8 resist to a series of plasma treatments. The formation of surface nano-nodules during oxygen plasma treatment explains the surface hydrophobicity. We have carefully evaluated the effects of the electron beam writing dose and the design of the exposure area with respect to the inclined angle of the fabricated structure.